Microscope questions (fine adjustment and light)?

The fine adjustment very slowly changes the distance between the objective lens and the object you are viewing. The coarse adjustment changes that distance quickly. You use the fine adjustment only when viewing something at the higher magnifications. You increase the light intensity when going from lower power to higher power objectives because the high power lenses are smaller in diameter, and therefore at any given light setting cannot take in as much light as the lower power lenses.